We present the results obtained from analysis of two AstroSat observations of the high mass X-ray binary pulsar OAO 1657-415. The observations covered 0.681–0.818 and 0.808–0.968 phases of the \(\sim \)10.4 day orbital period of the system, in March and July 2019, respectively. Despite being outside the eclipsing regime, the power density spectrum from the first observation lacks any signature of pulsation or quasi-periodic oscillations. However, during July observation, X-ray pulsations at a period of 37.0375 s were clearly detected in the light curves. The pulse profiles from the second observation consist of a broad single peak with a dip-like structure in the middle across the observed energy range. We explored evolution of the pulse profile in narrow time and energy segments. We detected pulsations in the light curves obtained from 0.808–0.92 orbital phase range, which is absent in the remaining part of the observation. The spectrum of OAO 1657-415 can be described by an absorbed power-law model along with an iron fluorescent emission line and a blackbody component for out-of-eclipse phase of the observation. Our findings are discussed in the frame of stellar wind accretion and accretion wake at late orbital phases of the binary.

我们展示了从对高质量 X 射线双星脉冲星 OAO 1657-415 的两个 AstroSat 观测结果的分析中获得的结果。观察结果涵盖了\(\sim \) 的0.681–0.818 和 0.808–0.968 阶段该系统的轨道周期为 10.4 天，分别在 2019 年 3 月和 7 月。尽管在日食范围之外，第一次观测的功率密度谱没有任何脉动或准周期振荡的特征。然而，在 7 月的观测中，在光变曲线中清楚地检测到了 37.0375 秒的 X 射线脉动。第二次观察的脉冲轮廓由一个宽的单峰组成，在整个观察到的能量范围的中间有一个类似倾角的结构。我们探索了窄时间段和能量段中脉冲轮廓的演变。我们在从 0.808-0.92 轨道相位范围获得的光曲线中检测到脉动，这在观察的其余部分中是不存在的。OAO 1657-415 的光谱可以通过吸收幂律模型以及铁荧光发射线和观测的失食阶段的黑体分量来描述。我们的研究结果是在双星轨道晚期阶段的恒星风吸积和吸积尾流的框架中讨论的。